gistfile1.java

public static Map<String, Collection<InboxEntry>> partitionByTaskName(Collection<InboxEntry> delegated)
    // unfortunately generalizing this requires a higher order function and java makes me not really want to bother
    // implementing default-dict correctly also needs a higher order function (default value constructor)
{
    Map<String, Collection<InboxEntry>> taskMap = new HashMap<String, Collection<InboxEntry>>(); // this is a default-dict
    for (InboxEntry inboxEntry : delegated)
    {
        // the partition key
 	String task_name = inboxEntry.getQueueItemAttributes().fetchSimpleValue("task_name");

 	Collection<InboxEntry> inboxEntries = taskMap.get(task_name);
 	if (null == inboxEntries)
 	{
 	    inboxEntries = new ArrayList<InboxEntry>();
 	    taskMap.put(task_name, inboxEntries);
 	}

 	inboxEntries.add(inboxEntry);
    }
    return taskMap;
}

public static <T, K> Multimap<K, T> partitionBy(final Iterable<? extends T> inputList, final Function<? super T, ? extends K> partitionFunc) {
        final Multimap<K, T> multimap = HashMultimap.create();
        for (T t : inputList) {
            multimap.put(partitionFunc.apply(t), t);
        }
        return multimap;
    }